Tentacles are multifaceted organs found in many aquatic invertebrate groups. In bivalves, tentacles are diverse, performing protective and sensory roles in numerous taxa with different ecologies. Such diversity is particularly accentuated in Pteriomorphia, a clade comprising scallops, oysters, file clams, and relatives. However, little is known about the evolution of these organs and their role in bivalve radiation. To test hypotheses of convergent tentacular evolution and possible association between tentacles and body orientation on the substrate, we first examined tentacle morphology in 108 preserved species representing 15 families across Pteriomorphia. Morphological descriptions of tentacle type (inner mantle fold tentacles – IFT; middle mantle fold tentacles – MFT) and position (marginal and submarginal) are provided, expanding the knowledge of less studied bivalve taxa. Then, we placed the morphological dataset under a molecular phylogenetic framework to estimate ancestral states. IFT likely had four independent origins, while MFT emerged twice independently. After being gained, tentacles have not been lost. In addition, evolution of MFT coincides with transitions in body position with the midsagittal plane parallel to the substrate in the clades of scallops (Pectinida) and oysters (Ostreida). Such a shift could be related to the increase of mantle exposure, favoring the emergence of serially repeated organs, such as tentacles. Altogether, our results support the convergent evolution of tentacles across different taxonomic levels, contributing to elucidate the diversification of bivalve anatomy.